1. Field of the Invention
The present invention pertains to wind-driven power generation (e.g., electrical power generation) in a water-based environment, and is particularly applicable to the placement of windmills on oceans and other deep bodies of water. The term “windmill” is used herein to mean any apparatus that converts wind energy to useful mechanical energy (typically, rotational mechanical energy).
2. Description of the Related Art
A fairly significant amount of effort has been directed toward generating usable energy from wind power. The advantages of wind power over competing potential energy sources are clear, i.e., wind power is a clean and renewable energy source. However, the costs of wind-powered energy generation often are significantly higher than the costs of alternative energy sources.
The most common conventional implementation of a wind-powered energy generation plant is a windmill farm, which involves the construction of a cluster of windmills on a fairly large area of land. An example is the windmill farm just outside of Palm Springs, Calif. Typically, a land-based windmill, such as is used in a windmill farm, has a plurality of elongated radially extending blades (or vanes) attached to a central rotor. Wind causes the vanes to rotate, turning the rotor, and this rotational energy is conveyed to an electrical generator, which in turn converts such kinetic rotational energy into electrical power.
This type of windmill is a horizontal-axis windmill, because the blades rotate about a horizontal axis. Less common are vertical-axis windmills in which the blades rotate about a vertical axis.
In order to be cost-effective, a windmill farm generally requires a large area of land in a location where strong (and preferably consistent) winds are present. However, very few such locations are available, particularly near the locations where power is needed most (e.g., in large cities or near certain manufacturing facilities). Moreover, where such potential windmill farm sites are available, it may be difficult or costly to obtain the necessary use permits that would enable one to construct a windmill farm.
In response to these difficulties, a number of proposals have been made to implement ocean-based (or other water-based) windmill facilities. Unlike land-based implementations, a water-based windmill often is of the vertical-axis turbine type. Beyond specified distances from the shore, an ocean-based wind-powered energy-generating facility generally will not require government permits. In addition, the large, unobstructed ocean areas provide an ideal environment for strong and consistent winds. However, these same conditions also give rise to more severe storms than generally are encountered on land. Such weather conditions and the potential for large and severe wave conditions make it difficult to construct a power generation facility that can avoid significant damage or destruction and thereby operate over the long term.